The disclosure of Japanese Patent Applications No. 2000-313961 filed on Oct. 13, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a reclining device, and more particularly to the setting of a free zone of a seat back.
2. Description of Related Art
A reclining device of a certain type is constructed as follows. First of all, a pawl having outer teeth on the side of a leading end thereof is brought into mesh with inner teeth of a ratchet on the side of an inner periphery thereof, so that a seat back is locked with respect to a seat cushion. Then, the seat back is unlocked with respect to the seat cushion by bringing the pawl out of mesh with the ratchet, so that the seat back can be tilted.
A reclining device of this type makes it possible to enhance locking strength of the seat back with respect to the seat cushion by enhancing meshing strength between the pawl and the ratchet. Therefore, as proposed, e.g., by Japanese Patent Application Laid-Open No. 6-125821, there is a reclining device employing a plurality of pawls to enhance meshing strength between the pawls and a ratchet. The reclining device of this type necessitates a range where the pawls are out of mesh while the ratchet is within a predetermined angular range, i.e., a free zone. The reclining device proposed by the aforementioned publication adopts a means of forming a free zone by introducing an unlatching ring.
In the reclining device of this type, the meshing strength between the pawls and the ratchet can be enhanced in proportion to an increase in the number of pawls to be employed. However, if the number of pawls is increased, a convex portion for setting a free zone cannot be formed on the unlatching ring for bringing the pawls out of mesh. This is because the convex portion for setting a free zone of a certain one of the pawls is located at a position where the pawls adjacent thereto are to be brought into mesh. This problem becomes all the more serious as the number of pawls increases or as the angular range of the free zone widens.
It is an object of the invention to make it possible to set a free zone in a reclining device of the aforementioned type and thus install a greater number of pawls and enhance meshing strength between the pawls and a ratchet even if an angular range where a certain one of the pawls is to be brought out of mesh with the ratchet and an angular range where the pawls adjacent to the certain one of the pawls are to be brought into mesh with the ratchet overlap with each other in a plan view, i.e., even if the sum of the angles to be set to bring the pawls into mesh and the angles to be set to bring the pawls out of mesh exceeds 360xc2x0.
A reclining device according to one aspect of the invention comprises a plurality of pawls, a ratchet, a holder, a cam body and an unlock member. The pawls have first teeth. The ratchet has a second teeth engaging the first teeth. The holder rotates concentrically with respect to the ratchet and holds the pawls such that the pawls can move toward and away from the second teeth of the ratchet. The cam body prevents the holder and the ratchet from rotating relative to each other and moving the pawls toward the ratchet to bring the pawls into mesh with the ratchet, and allows the holder and the ratchet to rotate relative to each other and moving the pawls away from the ratchet to bring the pawls out of mesh with the ratchet.
The reclining device according to another aspect of the invention comprises an unlock member that holds at least one of the pawls while the holder and the ratchet form a relative rotational angle of a predetermined range and that brings the at least one of the pawls out of mesh with the ratchet. The sum of all angles to be set to bring the pawls into mesh or out of mesh exceeds 360xc2x0.
In the reclining device according to another aspect of the invention, the unlock member may have a hole for engagement with a protrusion portion formed on the at least one of the pawls. The unlock member may rotate together with the ratchet. The unlock member may engage the protrusion portion of the at least one of the pawls within a free zone angular range of the at least one of the pawls.